According to a report in the Daily Telegraph:
The taxman is fast-tracking aggrieved members of the public through to a hearing to hammer out a settlement within a few hours.
The one-day hearing involves a mediator, either an HMRC employee or an independent third party, listening to both sides of the story in an attempt to unlock the stalemate between the taxpayer and the Revenue. The mediator’s aim is to reach a settlement during the course of the day.
The new mediation scheme had a low-key roll out at the end of last year and is aimed at small businesses and individuals with large tax bill disputes, in order to clear the backlog of disputes facing HMRC.
How to take advantage of an ADR
You can apply for ADR if you have stopped making progress in your dealings with HMRC - more details can be found here. But a word of caution, reports suggest that only 1 on 2 cases are resolved in a day.